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It worked...
So which pictures? Thematic or beauties (natural) from my island?
Let's stick to two stroke
Above is 2016 and 2017 winning moped cup cylinder, my first question is about the ports added between main exhaust and A ports ( forget about exh boost ports, they were added later on and added short circuiting) I used to call them golmans, like to prevent or slow down a bit mixture from rest of the transfer ports from going to exhaust. Timing of these subA ports was half of the A ports which are 126° angled 10°, B 130 ° angled 70° and C 132° angled 70°upward. So B and C are heading torwards cylinder head...exhaust 168°.
Any similar idea or comment?

RC car engines have used transfer ports somewhat like that. They use Yam 12 (very poor) transfer passage shapes, though. We were able to improve the power of a 35 cc race engine with the pictured liner modification. The stock liner is on the left. The best power modification is the second liner from the left. All these designs try to block the flow out of the exhaust. I think the RC car liner designs may also be for marketing more than serious performance improvement. They come out with different porting every few years.

not a lot of updates to report but im still chipping away at it every chance I can. exh passages are welded on and now its just a bunch of grinding away the existing outer shell and extend the aux ears to the end of passage. maybe the exh spigot would of been fine with three bolts attaching it to the cyl but I decided to use four

Above is 2016 and 2017 winning moped cup cylinder, my first question is about the ports added between main exhaust and A ports ( forget about exh boost ports, they were added later on and added short circuiting) I used to call them golmans, like to prevent or slow down a bit mixture from rest of the transfer ports from going to exhaust. Timing of these subA ports was half of the A ports which are 126° angled 10°, B 130 ° angled 70° and C 132° angled 70°upward. So B and C are heading torwards cylinder head...exhaust 168°.

What kind of transmission are you using Frano? Gearbox, CVT, centrifugal clutch?

thank you sir. without any cutting or welding I believe these cylinders do a bit over 100hp on methanol, that's what ive heard any way. but I think I can do better than that. if nothing else, atleast Ill gain more welding and fabrication experience for later down the road on other projects . theres a few more things I wanted to do , like raise the exh floor since its so low but that would add a fair bit more time so I decided against it. transfers have very little up angle going into the cyl so ill likely put epoxy in there. ill keep updating as I go, will have five more days off work next week and should be able to make quit a bit more progress

Frits, this one was ordinary gearbox, clutch ratio 4.07 ,1st ratio 3.8 ,2nd 2.28, 3rd 1.59,4th 1.24, 5th 1.07
So porting and everything else is done starting from gearbox ratios which cannot be changed ( rulebook you know hehe)
This one is from two stage centrifugal clutch, but with reed valve same arrangement ( later converted to piston induction for much better performance, can you imagine that!?...rulebooks again)

Lhoring, I can see that transfers open at the same time? Wouldn't be better to flow them much last to let A,B and C's do the scavenging?
Greetings to all!

... the ports added between main exhaust and A ports... I used to call them golmans... Timing of these subA ports was half of the A ports...

Frano, calling your golmans 'subA ports' may cause some confusion. The convention is that the transfer ports closest to the main exhaust port are called the A-ports. Any additional sets of ports are then called B-ports, C-ports, and so on. So in your case the 'golmans' are the A-ports.

thank you sir. without any cutting or welding I believe these cylinders do a bit over 100hp on methanol, that's what ive heard any way. but I think I can do better than that. if nothing else, atleast Ill gain more welding and fabrication experience for later down the road on other projects . theres a few more things I wanted to do , like raise the exh floor since its so low but that would add a fair bit more time so I decided against it. transfers have very little up angle going into the cyl so ill likely put epoxy in there. ill keep updating as I go, will have five more days off work next week and should be able to make quit a bit more progress

Originally Posted by teriks

Thats one hell of an effort, hope it pays off!

some time ago I found this photo but im following the same design they have done with the exh duct. im doubling its length (original was only 1x bore diam). also extending ears to the spigot . effective area at bore face will reduce to 75% at spigot exit. and the whole thing will be cooled from water. with other engines the exh is far to short because the chassis cant allow anything longer but now I have no chassis compromise and its free to do as I wish

Frits: You've posted a new version of your Transfer Axial Angle formulae on another forum.
While the A transfer angle stays the same, the B port angle is different and the Boost Port angle is markedly different.
Can I just ask you to confirm that this is not an error, before I go ahead and cut to the new formulae?

750 Waterbucket

Anyone got a GT750 cylinder and head I could look at.
I have a possible job to model a billet head with inserts as no one it seems has done this before.
And as with the RD/TZ the water route needs changing.
Please PM if you can help.

Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

Some results from testing with direct intake from carb to transfers windows ( via crankcase )on Honda NS cylinder.
It is just feelings from riding on the road ( no dyno ). Intake duration 210 degrees.

Starting is much easier than with std. and feels like engine work much cleaner at lower revs without flooding, even cold. There is no typical 1-2 gear flooding smoke at the start of riding, its more like with four stroke.

Max power with Std feels little higher at 11000 rpm and then drops, but in the power band with direct intake, power feels more linear from 11000 to 13000 rpm , again more like on 4t and about 750 revs more than std.

Engine reaction to higher intake duration ( 245 degrees ) very interesting. Feels like lost power everywhere and at 12000 rpm engine stopped and then again revs up ( add drawing)

Frits: You've posted a new version of your Transfer Axial Angle formulae on another forum.
While the A transfer angle stays the same, the B port angle is different and the Boost Port angle is markedly different.
Can I just ask you to confirm that this is not an error, before I go ahead and cut to the new formulae?

You are right, it was a mix-up of old and new versions. Thanks for pointing it out. Here is the correct version.